Control system



L. W. THOMPSQN ET AL CONTROL SYSTEM Filed Dec. 16, 1930 Inventors: Louis\Xl. Thompson, Edward H. Horstkotbe by W (A4.

Their Attorney.

Patented Nov. 29, 1932 UNITED STATES PATENT ()FFICE LOUIS W. THOMPSON,OF SCHENECTADY, NEW YORK, AND EDWARD H. HORSTKOTTE,

OF ERIE, PENNSYLVANIA, ASSIGNORS TO GENERAL ELECTRIC COMPANY, A CORPO-RATION OF NEW YORK CONTROL SYSTEM Application field December 16, 1930.SerialNo. 502,738.

This invention relates to'contro-l systems, more particularly to systemsfor controlling the operation of electric motors, and has for an objectthe provision of a simple, reliable and efficient system of the kind.

More specifically the invention relates to control systems for pluralmotor drives for paper making machines, printing presses and the like,wherein aplurality of elements are required to operate in apredetermined relationship with respect toeach other and a furtherobject of the invention is to provide a speed regulating system formaintaining a constant speed ratio between the elements that shalleffect a change or adjustment in the basic speed of the drive withoutdisturbing the speed ratio between the elements.

It is known that the speed of operation of a regulator for maintaining acharacteristic of a dynamo electric machine constant at a desired valuevaries in accordance with the magnitude of the value of thecharacteristics that is being held. Thus, in the case of a speedregulator for a motor the operation of the regulator when maintaining aslow speed, for example 200 R. P. M. is very slow, whilst whenmaintaining a. higher speed, for example 1,000 R. P. M. the action ofthe regulator is exceedingly fast. It will thus be seen that in a.plural motor drive for a paper making machine and the like the action ofa speed regulator for one of the sectional motors at low basic speeds ofthe drive may be'so sluggish as to cause a breakage in the paper beforethe speed can be restored to the correct value, and likewise at highbasic speeds, the action of the regulator may be so fast and erratic asto cause hunting of the motor and consequently a breakage of the paper.Accordingly a further object of the invention is the provision of aregulating system by means of which a uniformly good control can beobtained throughout the entire' speed range of I the drive.

In carrying the invention into effect in one form thereof we provideregulators having a pressure responslve resistance connected in circuitwith .adynamo electric machine for controlling an'operatingcharacteristic there of, together withmeans for controlling the over theentire speed range of the motor.

In illustrating the invention in one form thereof we have shown it asembodied in a sectional motor drive employed to operate a sectionalizedpaper making machine, printing press or the like in which a purality ofelements are required to run in fixed speed relationship with respect toeach other. For a better and more complete understanding of theinvention reference should now be had to the following specification andto the accompanying drawing the single figure of which is adiagrammatical representation of an embodiment of the invention.

Referring now to the drawing the rolls 10, 11 of a sectionalized machinesuch for example as a paper making machine are driven by means ofsuitable electric motors 12, 13 respectively to the drive shafts 14, 15of which the rols are connected by means of any suitable drivingconnections. In the drawing, the rolls 10, 11 are shown mounted directlyon the drive shafts to the motors.

The motors 12, 18 are shown as separately excited direct current motors,the respective armature members 16, 17 of which are supplied with directcurrent from any suitable source of direct current supply such forexample as a direct current generator 18 which is connected to thesupply buses 19, 20 by means of conductors 21 the armature of motor 16being connected to the supply buses 19, 20 by conductors 22 and thearmature 17 of motor 13 being connected to the same supply buses 19, 20by the conductors 23 as shown in the drawing.

The supply generator 18 is driven by any suitable driving means such forexample as the alternating current electric motor 24 which in turn issupplied with alternating current from any suitable source such as thepoly-phase source represented in the drawing by the three supply lines25 to which the terminals of the mot0r'24 are connected by conductors 26as shown. As previously stated the motors 12, 13 are shown as separatelyexcited motors; they being respectively provided with separately excitedfield windings 27, 28 which are supplied from any suitable directcurrent source, represented in the drawing by the exciter 29, thearmature, of which supplies the constant excitation busses 30, 31 towhich the field winding 27 is connected by conductors 32, 33 and towhich the field winding 28 is connected by means of conductors 34, 35. I

The exciter 29 is driven at a speed which is preferably substantiallyconstant by any suitable driving means such for example as thatrepresented in the drawing by the alternating current motor 37 which issupplied with alternating current from any suitable supply source suchfor example as that represented in the drawing by the three conductors38 to which the terminals of the motor 37 are connected by means of thethree conductors 39. The exciter 29 is self excited; it being providedwith a field winding 30, the opposite terminals of which are connectedto the armature terminals of the exciter in series with an adjustableresistance 41 by means of which the generated voltage of the exciter maybe adjusted as desired to provide the correct excitation for the fieldwindings 27, 28 of the drive motors 12, 13.

The speed of the drive motors 12, 13 may be varied over a wide rangeofbasic values by varying the terminal voltage of the suptbi' controlledrheostat 42 is provided for varying the excitation of the separatelyexcited field winding 43 of the supply generator 18; the field winding43 being in turn supplied from the constant voltage excitation busses30, 31 from which the field wind-Y ings 27 and 28 of the drive motorsare supplied.

As shown in the drawing the motor controlled rheostat 42 comprises avariable resistance 44, a stationary contact 45 and a movable contact 46which bridges the resistance and the stationary contact 45. The movablecontact 46 is operated either in an upwardly or a downwardly directionto vary the amount of the resistance 44 in circuit with the fieldwinding 43 by any suitable driving means such for example as the smallelectric pilot motor 47 to the drive shaft of which the movable contact46 is connected by means of the bevel gearing 48 and a screw member 49;the contact 46 being provided with threads which engage the threads ofthe screw member 49. The pilot motor 47 is supplied with generator 18,and for this purpose a moelectric energy from any suitable source ofpower such for example as the busses 19, 20 which are supplied from thegenerator 18 and to which the terminals of the pilot motor 47 areconnected by means of the conductors 51 and 52. It will be observed thatthe pilot one direction, for example the forward direction, and the pushbutton 56 serves to connect the armature of the motor to the supplybusses with the field windings 54' in circuit to provide for rotation ofthe motors in the opposite or reverse direction. It will thus beobserved that the speed of the drive motors 12, 13 may be increased ordecreased as desired simply by depressing either of the switch buttons55, 56 to decrease or increase the amount of the resistance 44 andthereby increase or decrease the terminalvoltage of the supply generator18.

The supply generator 18 and theflmotors 12, 13 supplied therefromcomprise a Ward- Leonard system and it will be understood by personsskilled in the art that a system of this type has a very wide speedrange the ratio between top and bottom speeds being approximately 10-1.In order that'the separate elements 10, 11 located. at the varioussections of the paper making machine may be niade to operate inpredeter- -mined relationship with each other at any speed within such awide range between the top and bottom values it is necessary that a veryflexible s eed regulating arrangement be provided t e speed regulatingsystem shown in the drawing comprising separate inductive devices 57, 58operatively associated with the drive motors 12 and 13 respectively, amaster frequency set 59, and separate speed regulating units 60 and 61,one unit for each section of the drive, and separate electricaldifierential devices 62, 63 for actuating the regulating units inresponse to the existence of a differential relationship between themaster inductive device 59 and the separate inductive devices 57, 58located at the various sections of the drive.

Since the separate'inductive devices 57, 58 located at various sectionsof the drive are in all respects identical with each other only theinductive device 57 will be described in de tail. This device comprisesa rotor member 64 and a stator member 65 each provided with windings ininductive relationship with each other. The winding (not shown) on the-'rotor member 64 is preferably a single phase represented in thedrawing by the supply con- 13 operate.

ductors 66 to which the terminals of this winding are connected by theconductors 67. A rotor member 64 is driven at a speed which isproportional to the s eed of the drive motor 12 to the drive sha t ofwhich it is connected by any suitable connecting means such for exampleas the variable speed arrangement shown in the drawing as comprising thecone pulley 68 mounted on the drive shaft out the motor 12 the conepulley 69 mounted on the shaft of rotor member 64 and the connect ingbelt @965 which may be shifted to any desired position on the pulleys bya suitable belt shifting means (not shown). The inductive device 58comprises similar elements similarly connected with the drive motor 13.

The master set 59 comprises an inductive device 71 having a rotor member72 provided with a single phase winding (not shown) supplied from thesingle phase source 66 to which the terminals of this single phasewinding are connected by means of the conductors 70, and a stator member73 provided with a distributed poly-circuit winding not shown) ininductive relation with the single phase winding on the rotor member.The rotor member is driven by a suitable driving means shown in thedrawing as a separately excited direct current motor 7 2 having a fieldwinding 75 supplied from the constant excitation busses 30, 31 to whichit is connected by the conductors 76 and having its armature mem bersupplied with direct current from the supply busses 19, 20 to which itis connected by means of the conductors 17 as shown.

The terminals of the poly-circuit windings on the stator member "Z3 areconnected to supply the regulating busses 78 and consequently thesebusses are energized with a poly-phase alternating voltage having a frequency proportional to the speed at which the rotor member 7 2 isdriven. It will thus be clear that since the pilot motor 7% which drivesthe rotor 72 is supplied from the variable voltage busses 19, 20 fromwhich the sectional drive motors 12, 13 are supplied that the frequencyof this alternating polyphase voltage at the busses 78 will beproportional to the speed at which the motors 12, It will also beunderstood that when the motor controlled rheostat 42 for the supplygenerator 18 is operated to increase or decrease the terminal voltage ofthe supply generator so as to increase or decrease the speed of themotors 12, 13, that the speed of the pilot motor 74 will likewise beincreased or decreased in proportion and as a result the frequency ofthe voltage at the busses 78 will also be increased or decreased inproportion. V i

The differential electrical device 62 comprises a stator member 79having a poly-circuit winding (not shown) which is connected to thetermmals of the poly-circuit winding on the stator member 65 ofinductive device skilled in the art will understand that since the rotormembers 64 of the inductive device 57 is driven by the motor 12 at aspeed proportional thereto that there will be induced in the winding onthe stator member 65 a poly-phase voltage having a frequencyproportional to the speed of the motor 12. Since the terminals of thewindings on the stator member 65 are connected to the terminals of thewindings on the stator member 7 9 of the differential device, thislatter winding will set up a rotating magnetic field which rotates inspace at a speed proportional to the frequency of the current suppliedthereto and consequently to the speed of the motor 12. It will also beclear that since the poly-circuit winding on the rotor member 80 of thedifferential device is supplied tromthe regulating busses 78 that thislatter winding will also set up a rotating nlagnetic field which willrotate in space at a speed proportional P to the speed at which themotors 12, 13 operate. By shifting the belt 69a in one direction or theother upon the cone pulleys 68, 69 the frequency of the poly-phasevoltage supplied to the winding on the stator member 79 can be made toexactly equal the frequency of the poly-phase voltage supplied to thewinding on the rotor member 80 when motor 12 is rotating at a desiredspeed. When this condition obtains the rotating magnetic field producedby the windings on the stator memher will rotate in space at exactly thesame speed as the rotating field which is produced by the winding on therotor member and consequently there will be no tendency what soevcr forthe rotor member 80 to rotate relatively to the stator and the latterwill remain at rest. However, should the phase relationship between thealternating voltages supplied to the windings on the rotor and statormembers of the differential device tend to change the phase relationshipbetween the axes of the rotating magnetic fields produced by thesewindings will likewise tend to change but this will cause the currentsupplied to these windings to increase to such an extent that a torquewill be developed'between the rotor and stator members and retation ofthe rotor member will ensue in such a direction as to maintain thesynchronous all respects identical only the device 60 wilt-fbe describedin detail. This device comprises a pressure responsive resistance (shownin the motor 47.

which the adjustable fulcrum member 84 can be moved back and forth tovary the lever ratio between thecam 85 and the carbon pile resistance 82and thus to require a greater or a lesser rotation of the cam 85 toeffect a predetermined change in the resistance ofthe carbon pile. Aspreviously pointed out in the specification the action of the speedregulator of the type so far described will be sluggish when maintaininga slow speed of the motor such for example as 200 R. P. M. and will beunduly fast and erratic when holding a high speed of the motor such'forexample as 1500 R. P. M. In order to overcome this disadvantage, weprovide means for varying the position of the fulcrum 84 in the slot 87in accordance with adjustments in the speed of the drive andthereby tomodify the regulating action i. e. the speed of operation of theregulator. The means shown comprises an electrical angular motionreceiving device 88 and an electrical angular motion transmitting device89 driven by the pilot The motion transmitting device 89 comprises arotor member 90 mounted on the drive shaft of the pilot motor 47 andprovided with a single phase Winding (not shown) supplied from anysuitable single phase source such for example as that represented by theconductors 66 to which it is connected as shown, and a stator member 91provided with adistributed poly-circuit winding (not shown) theterminals of which a are connected to the busses represented in thedrawing by the conductors 92. The motion receiving device 88 is providedwith. a rotor member 93, a stator member 94; the rotor member beingprovided with a single phase winding which is supplied from the samesingle phase source as that from which the windings on the rotor member90 of the transmitting device is supplied and the stator member 94 isprovided with a distributed '7 poly-circuit winding, the terminals ofwhich are connected to the busses 92 by means of the conductors 96. Asshown in the drawing the rotor member is mounted upon a shaft 97 whichhas an elongated threaded portion extending beneath the lever arm 83 andas shown it engages a nut 98 in which is mounted a movable fulcrummember 84. Persons skilled in the art will understand that the singlephase winding upon the rotor member '90 of the motion transmittingdevice induces alternating voltages in the winding on the rotor member91 which are supplied to the busses 92 and likewise that the Winding onthe rotor member 93 of the motion receiving device induces voltages inthe winding on the stator member 94 which are likewise supplied to thebusses 92. As long as the axes of the rotor windings on both thetransmitting and receiving devices occupy similar positions relative tothe poly-circuit stator windings the voltages induced in these statorwindings will be equal and opposite and consequently a minimum ofcurrent will flow in the stator windings. However, as soon as the axisof the winding of the rotor member 90 of the transmitting device ismoved relatively to the axis of the winding on the stator member thisbalanced relationship of the voltages will be disturbed and consequentlycurrents will be set up in the winding on the stator member 94 of themotion receiving device and consequently a torque will be caused toexist between the rotor and stator members of the motion receivingdevice and the rotor member will rotate through the same number ofelectrical degrees as the winding on the motion transmitting device.When the rotor member 93 of the receiving device has been rotatedthrough the same number of electrical degrees as the rotor member 90 ofthe transmitting device, the balanced relationship between the voltageinduced 1n the stator windings of these devices will again obtain and nofurther motion of the rotor of the receiving device will take place. Itwill be clear that rotation of the rotor member 93 of the transmittingdevices causes the nut 98 to be actuated in one direction or anotheralong the threaded shaft 97 and thus to shift the fulcrum 84 of thelever 83.

The elements and connections of the regulating device 61 and also theregulating devices of all succeeding sections of the drive are exactlyidentical with those of the regulating device 60 which has just beendescribed in detail. a With the above understanding of the elements, andthe manner in which they are connected or associated with each other theoperation of our system will readily be understood from the detaileddescription which follows:

It will be assumed that the electric motor 24 which drives the generator18 and the electric motor 37 which drives the exciter 29 have both beenstarted up by suitable starting devices (not shown) and that thegenerator 18 is supplying voltage to the supply busses 19, 20 while theexciter 29 is likewise supplying voltage to the busses 30, 31. Theposition of the movable contact 46 on the resistance 44 indicates thatthe excitation of the generator 18 is about half way between the maximumand minimum values and that consequently the generated voltage andlikewise the speeds of the drive motors 12, 13 at the various sectionsof the drive are operating at a speed approximately half way between theminimum and maximum speed values. As previously pointed out the pilotmotor 74 drives the rotor member 72 of the inductive device 71 at aspeed proportional to that at which the sectional drive motors 12, 13are operating and consequently itwill supply an alternating poly-phasevoltage to the busses 78 which in turn is supplied to the poly-phasewinde ings on the rotor member 80 of the electrical differential device62. Likewise the rotor member 64 of the inductive device 57 which isdriven by the drive motor 12 supplies an alternating poly-phase voltageto the polyphase windings on the state: member 79 of the diitferentialdevice. The voltages supplied to the windings on the rotor and statormembers of the differential device cause rotating magnetic fields to beset up by each of these windings and as long as the axes of the windingson the rotor members til and the rotor member 72 remain intheir-predetermined relationship with each other the current flowing inthe windings on the above rotor and stator members of the ditleren'tialdevice will be minimum and the rotating magneto fields set up by thesewindings will remain in a fixed relationship with respect to each.other. This relationship will obtain as long as the drive motor 12operates at the desired speed. i

Should the speed of the motor 12 decrease for any reason whatsoever,such for example as a sudden increase in load on the element 10 the axisof the winding on the rotor mem-- till ber 64 will tend to lag the axisof the winding on the rotor member 72 and consequently the axis of therotating magnetic field set up by the windings on the stator member 79of the differential device will tend to lag the axis or the rotatingmagnetic field set up by th windings on the rotor member of thediii'erential device. As a result of this the current in the windings onboth the rotor andstator members of the diilerential device willincrease and will cause a suflicient torque to exist between the rotorand stator members which will cause the rotor member 800i theditlerential device to rotate in such a direction as to operate the cammember 85 in a clockwise direction thus permitting the lever 83 torotate in a clockwise direction and thus to lessen the pressure on theresistance of the carbon pile 82. This lessening of the pressure on thecarbon pile 82 results in an increase in its ohmic resistance andconsequently in a decrease in the current flowing in field winding 27 ofthe motor 12 which causes the motor to increase its speed. This actioncontinues until the speed of motor 12 has increased to its tormenvalueat which time the axes of the windings on the rotor members 64 and 72will again be in step with each other and likewise the axes of therotating magnetic fields set up by the windings on the stator member 79and rotor member 80 of the diflerential device willbe in step with eachother and consequently there will be no torque existing between thestator and rotor of the difi'erential device and the motion of therotorwill cease.

Persons skilled in the art will understand that had the speed of themotor 12 increased for any reason such for example as a sudden decreasein the load on the element 10 the action of the regulating device wouldhave been exactly the opposite of that described above. Likewise itwillbe clear that had the speed of the motor 13 or any oil the otherdrive motors at the succeeding sections of the drive increased ordecreased the action of the regulating device located at that parti ularsection of the drive would have been exactly the same as that justdescribed for the motor 12;

Now let it be assumed it is desired to increase the basic speed oi? thedrive, i. e., simultaneously increase the speed of all the drive motors12, 13 etc. Depression of the start button which controls the operationof the rheostat motor 47 causes the armature and difi erential fieldwindings to be energized across the supply busses it) 20. there bycausing the motor 4-? to operate the movable contact member 46 in adownwardly direction so as to increase the excitation of t e generator18 and likewise to increase its generative voltage, This increase in thegem erated voltage of the generator 18 will increase the speed oi"? themotors 12-{3 which are supplied therefrom, as will be well understood bythose skilled in the art. Likewise the increase in the generativevoltage of the generator 18 will increase the speed of the pilot motor74 which drives the master inductive device 71, thereby causing thefrequency of the poly-phase voltage supplied by this device to theregulatin busses 78 to be increased in proportion. 'le increase in thespeed of the motorslh-lii, etc. will, of course increase the frequencyof the polypha se voltages supplied by inductive devices 57, 58 to thedifi'erential devices 52-63 in like proportion Consequently, the dr vellltl lltl motors-12l3 will operate at the desired 7 higher speed andthe rotor member 800 5 the differential device 62 will remain at rest aslong as the speeds of the motorsl2-l3remain at this desired higher valueOperation of the pilot motor 47 to increase the generator voltage of thegenerator 18 and the speeds of the motors 1213 also causes the rotor 90of the motion transmitting device 89.

to rotate and, as explained above, this results in rotation of the rotormembers of all the motion receiving devices, 83, 83 etc., at the Varioussections of the drive in such a direction that the fulcrum members 84, 8P- will be moved toward the right a distance which is proportional tothe number of rotations of the pilot motor 47 and consequentlyprbportional to the increase in speed of the driving motors 12-13 etc.

Now should the speed of the motor 12 for any reason, such for example asin increase in the load on the element 10, tend to decrease, the cammember 85 will be operated in the previously described manner in aclocKwise direction so as to permit movement of the lever 83 about thefulcrum 84: in a clockwise direction to lessen the pressure on thecarbon pile resistance 82 thereby increasing its ohmic value and alsoincreasing the speed of the motor 12. However because of the fact thatthe fulcrum 84: has now been moved 'to a position nearer to the carbonpile resistance and more remote from the cam member 85, the lever mustmove a greater distance in order toeffect the same change in the ohmicvalue of the resistance 82 than was the case when the fulcrum member 84was in the mid-position illustrated in the drawing and the motor 12 wasoperating at a lower basic speed. Consequently, the cam member 85 willbe required to move agreater distance in order to permit of thisincreased movement of the lever 83. It will thus be seen that as thespeed of the drive is increased, the operating speed of the regulatingdevices is decreased and thereby the tendency of the regulators to causehunting of the motors 12, 13 etc. at the higher speed of the drive isovercome.

Had the decrease button 56 been operated to decrease the basic speed ofthe drive, the operation would have been exactly the opposite of thatabove described which followed the operation of the increase button 55.In this event, the fulcrum of thelever arm of the regulating deviceswould be operated toward the left an amountproportional to the decreasein the speed of the motors 12-13 and as a result the cams which operatethese levers, would not have to travel as far to effect the same ohmicchange in the carbon pile resistances and consequently in the speeds ofthe motors 12-13 as was the case 'when the fulcrums of the lever armwere located further toward the right with the motors 12-13 operating ata higher speed; It Wlll thus be clear that since the cams 85 are onlyrequired to travel a small distance in order to effect the same ohmicchange in the carbon pile resistances that the operating speed of theregulators is increased as the speed of the drive is decreased.Consequently, the usual sluggishness of the regulators at low speeds ofthe drive is overcome and changes in the speeds of the drive motors12-13 will be effected as rapidly at the low speed as at intermediate orhigh speed.

It will thus be clear that we have provided means for modifying thespeed of operation of the'regulators in accordance with adjust ments inthe basic speed of the. drive motors 12-13 so that uniformly goodregulation is obtained at all speeds of the drive.

Although in accordance with the provisions in the patent statutes wehave described our invention as embodiedin specific apparatus andconnected in a particular manner, we would have it understood thattheinvention is by no means limited to the apparatus and connectionsshown since modifications and alterations will readily suggestthemselves to persons skilled in the art without departing from the truespirit of this invention or from the scope of the annexed claims.

What we claim as new and desire to secure by Letters Patent of theUnited States, is: 1. A control system comprising in combination adynamo electric machine, means for adjusting an operating characteristicof said machine to a plurality of values, regulating means comprising apressure responsive resistance and actuating means for said resistanceresponsive to an operating condition of said machine for maintainingsaid characteristic substantially constant, at a desired value, andmeans for modifying the action of said actuating means in accordancewith adjustments in the value of said characteristic.

2. A control system for a dynamo electric machine comprising means foradjusting a characteristic of said machine to a plurality of values, aregulator comprising a carbon pile resistance and means movable inresponse to variations in said characteristic for actuating saidresistance to maintain said characteristic substantially constant at thevalue to which said characteristic is adjusted, and means controlled bysaid adjusting means for modifying the movement of said regulating meansin accordance with the values to which justed.

said characteristic is ad- 3. A control system comprising a dynamoelectric machine having a field winding, means for ad usting anoperating characteristic. of saidmachine to one of a plurality ofdilferent values, a regulator having a carbon'pile resistance connectedin circuit with said field Windingand movable actuating means for saidresistance responsive to an operating condition of said machine formaintaining the characteristic of said ma 7 chine substantially constantatan adjusted value, and means responsive to operation of said adjustingmeans for controlling the speed of operation of said actuating means inaccordance with the values to which said characteristics are adjusted.

4. A control system comprising aidynamof electric machine, means foradjusting a characteristic of said machine to aplurality of values,regulating means forsaid machine comprising a variable resistance and amov able member controlled by an operating char o acteristic of saidmachine for controlling said resistance, and means controlled by saidcharacteristic adjusting means for controlling the movement of saidmember.

5. In a system of motor control, the combination with an electric motor,means for adjusting the speed of the motor to one of a plurality ofpredetermined values, a regulator comprising a pressure responsiveresistance and means operable in response to deviations of the speed ofthe motor from a desired value for actuating said resistance to restorethe speed of said motor to said desired value, and means for varying thespeed at which said actuating means operates in accordance withadjustments in the speed of said motor.

6. In a control system the combination with a dynamo electric machine ofmeans for adjusting a characteristic of said machine to a plurality ofvalues, means for producing a rotating magnetic field having apredetel-mined speed of rotation, means for producing' a second rotatingmagnetic field having a speed of rotation of predetermined re lationshipwith respect to the value of said operating characteristic of saidmachine, means comprising a movable member controlled by both saidmagnetic fields and a resistance controlled by the movement of saidmember for controlling an operating characteristic of said machine, andmeans for controlling the movement of said member in accordance withadjustments in the value of said characteristics.

7. A control system comprising an electric motor, means for adjustingthe speed of said motor to a plurality of values, means for producing arotating magnetic fieldhaving a predetermined speed of rotation meansoperated by said motor for producing a rotating magnetic field having aspeed of rotation of predetermined relationship with the speed of themotor, means comprising a movable member responsive to the phaserelationship of said magnetic fields and a pressure responsiveresistance connected in circuit With said motor and actuated by saidmember for controlling the speed of said motor, and means for modifyingthe movement of said memher in accordance with adjustments in the speedof said motor.

8. A control system comprising anelectl'ic motor, means for producing analternating voltage having a predetermined frequency, means operated bythe motor for producing an alternating voltage having a frequencyproportional to the speed of said motor, means comprising a movablemember responsive to the phase relationship of said voltages and apressure responsive resistance connected in circuit with said motor andcontrolled by the movement of said member for controlling the speed ofsaid motor, and means movable in accordance with adjustments in thespeed of said motor for modifying the movement of said movable member.

9. A system of motor control comprising an electric motor, means forproducing a r0- tating magnetic field having a predetermined speed ofrotation, means operated by the m0- tor for producing a rotatingmagnetic field having a speed of rotation proportional to the speed ofthe motor, means comprising a movable member responsive to a variationin the relative speeds of said magnetic fields and a pressure responsiveresistance connected in the field circuit of said mot-or and actuated bythe movement of said member for controlling said motor to maintain thespeed of said motor constant, means for adjusting the speed of saidmotor to a plurality of desired values, and means operated by said speedadjusting means for controlling the speedof the resistance actuatingmovement of said member.

10. Acontrol system comprising an electric motor, an electrical devicefor generating an alternating voltage of predetermined fro.- quency, asecond electrical device operated by the motor for generating analternating voltage having a frequency proportional to the speed of themotor, a pressure responsive resistance connected to said motor, meanscomprising an electrical differential device responsive to a variationin the phase relationship of said voltages and a movable elementcontrolled by said difl erential device for actuating said resistance tocontrol the speed of said motor, means for adjusting the e speed of saidmotors to a plurality of desired values, and means comprising anelectrical motion transmitting device driven by said speed adjustingmeans and an electrical motion receiving device connected to saidtransmitting device for controlling the movement of said movable member.

11. A motor control system comprising an electric motor, means foradjusting the speed otthe motor to a plurality of values, means forproducing an alternating voltage of predetermined frequency,meansfoperated by the motor for producing an alternating voltage havinga frequency proportional to the speed of themotor, a device movable inresponse to a variation in the phase relationship of said voltages, aresistance connected to said motor, a member movable in response tomovement of said device for controlling said resistance to maintain thespeed of said motor 12. A control system comprising an electric motor, aregulator for maintaining the speed of said motor constant at a desiredvalue, said regulator comprising a member movable about a fulcrum, adevice responsive to' a variation in the speed of said motorforactuating said member and a pressure responsive resistanceconnected incircuit with said motor and actuated by said member, means for adjustingthe speed of saidmotor to aplurality of desired values, and meanscontrolled by said adjusting means for shifting the fulcrum of saidmember so as to vary the speed of operation of said regulator inaccordance with adjustments in the speed of said motor. U

13. A control system comprising an electric motor, means for adjustingan operating characteristic of said motor to a plurality of values, aregulator for maintaining said characteristic constant at a desiredvalue, said regulator comprising acompressible resistan'ce in circuitwith said motor, a lever having an adjustable fulcrum, a cam for actu-'ating said lever and a device responsiveto a departure of saidcharacteristic from a desired value for actuating saidwcam, and meansresponsive to an operation of said characteristic adjusting means forshifting the fulcrum of said lever so as to change the operating speedof said regulator in inverse proportion to a change in the adjustment ofsaid characteristic.

14. A control system comprising an electric motor having a fieldwinding, a regulator for maintaining the speed of the motor constant ata desired value, said regulator comprising a member movable about afulcrum a device responsive to a variation in the speed of said motorfor actuating said member and a pressure responsive resistance connectedin circuit with said field winding and actuated by said ineznber,. meansfor adjusting the speed of said motor to a plurality of desired values,means comprisinga motion transmitting device operated by said adjustingmeans and a motion receiving device electrically connected with saidtransmitting device for shifting the fulcrum of said member so as tovary the operating speed of said regulator in accordance withadjustments in the speed of said motor.

15. A control system comprising a generator and a main ,motor suppliedtherefrom, a

regulator for maintaining the speed of the motor constant at a desiredvalue; said regulator comprising a member movable about a fulcrum, meansresponsive to a variation in the speed of said motor for actuating saidmember and a compressible carbon pile resistance connected in circuitwith said motor and arranged to be actuated by said memher, an auxiliarymotor and a rheostat actuated thereby for varying the voltage of said pI "section of the drive supplied from said gengenerator so as to adjustthe speed of said main motor to a plurahty of values, means driven bysaid auxiliary motor and a motion receiving device connected with saidtransmitting device for moving the fulcrum of said'member when the speedof said main motor is adjusted soas to vary the operating speed of saidregulator in accordance with adjustments in the speed of said mainmotor.v

16. A control system comprising an electric motor provided with a fieldwinding, a pressure responsive resistance connected in circuit with saidwinding, a movable memher having an adjustable fulcrum and arranged tocooperate with said resistance, means for adjusting the speed of saidmotor to a plurality of values, a device controlled by said adjustingmeans for generating a periodic voltage having a frequency proportionalto the desired speed of said motor, a device operated by said motor forgenerating a periodic voltage proportional to the speed of said motor,an electrical differential device responsive to a change in the phaserelationship between said voltages upon a deviation of the speed of saidmotor from a desired value for causing said member to actuate saidresistance so as to restore the speed of said motor to said desiredvalue, and means operated by said adjusting means for varying thefulcrum of said member in accordance with adjustments of the speed ofsaid motor.

17. A plural motor drive for paper making machines and the like whereina plurality of elements are required to operate in predeterminedrelationship with each other comprising a plurality of motors, means forproducing an alternating voltage of a frequency having a predeterminedrelationship with the desired speeds of said motors, a separateelectrical device operated by each of said motors for generating analternating voltage having a frequency proportional to the speed of theassociated motor, a separate electrical differential device associatedwith each of said motors for responding to varia tions in the phaserelationships between said first mentioned voltage and the voltagesproduced by said'electrical devices, a separate variable resistanceconnected in circuit with each of said motors, a separate membercontrolled by each of said difierential devices for actuating acorresponding one of said resistances to maintain the speeds of said m0-tors substantially constant, means for simultaneously adjusting thespeed of said motors to desired values, and means for slmultaneouslymodifying the action of said actuating members in accordance withadjusting machines and the like comprising a sup ply generator, aseparate drive motor for each erator, a separate inductive device drivenby each of said motors for generating an alternating voltage having afrequency proportional to the speed of the motor, an auxiliary motorsupplied from said generator and an inductive device driven thereby forgenerating voltage of a frequency having a predetermined relationshipwith the speeds of said motors, a separate electrical differentialdevice associated with each of said motors responsive to a variation inthe phase relationship of said voltages, a separate pressure responsiveresistance connected to each of said motors, a separate movable memberactuated by each of said differential devices for actuating one of saidresistances to hold the speeds of said motors constant, means comprisinga second auxiliary motor and a rheostat operated thereby for varying thevoltage of said generator to vary the speeds of all of said drive motorsand said first auxiliary motor simultaneously and means operated by saidsecond auxiliary motor for simultaneously varying the speed of operationof said members in accordance with adjustments in the speeds of saidmotors.

19. A sectionalized drive for paper making machines and the likecomprising a separate drive motor at each section of the drive, agenerator for supplying said motors, a separate regulator for each motorfor maintaining constant speed thereof, said regulator comprising apressure responsive resistance connected in circuit with said motor, alever having an adjustable fulcrum and arranged to actuate saidresistance, a cam for actuating said lever, and means responsive to avariation in a desired speed of said motor for actuating said cam, meanscomprising an auxiliary motor and a rheostat operated thereby forvarying the voltage of said generator to adjust the speeds of all ofsaid motors simultaneously, and means comprising a motion transmittingdevice driven by said auxiliary motor and a plurality of motionreceiving devices connected to said transmitting device, one of saidreceiving devices being located at each section of the drive andarranged to shift the fulcrums of said levers to vary the speed ofoperation of said regulators in accordance with adjustments in the speedof said motors.

20. A plural motor drive for paper making machines and the likecomprising a separate drive motor for each section of the drive, agenerator for supplying said motors, an auxiliary motor supplied fromsaid generator and an inductive device driven thereby for generating analternating voltage of a frequency having a predetermined relationshipwith a desired speed of said drive motors, a second auxiliary motor anda rheostat operated thereby for varying the voltage of said generator tosimultaneously and proportionally adjust the speeds of all of said drivemotors and the frequency of said alternating voltage, a separate speedregulator for each of said drive motors, said regulator comprising acarbon pile resistance connected in the field circuit of the associatedmotor, a lever having an adjustable fulcrum for actuating saidresistance, and a cam for actuating said lever, a separate inductivedevice driven by each of said drive motors for generating an alternatingvoltage havinga frequency proportional In witness whereof, we havehereunto set our hands this 12th day of December, 1930,

and this 13th day of December, 1930.

LOUIS W. THOMPSON. EDWARD H. HORSTKOTTE.

